Typical load bearing or separation wall assemblies in buildings are made of support structures, for example, wooden or metal studs, covered by wallboards. There are many different types of wallboard for use depending on the requirements of various applications. One wallboard type that is most commonly used to build internal walls in buildings is gypsum wallboard, which is conventionally attached to studs. Gypsum wallboards are available in various standard sizes having predetermined width, for example, 4 ft., and predetermined lengths such as 8 ft., 10 ft., or other sizes. In conventional installations, wallboards are assembled end-to-end and/or side-to-side to cover wall surfaces greater than the length or width of the drywall sheets, which requires joints along edges of wallboard sheets to be created.
Typical wallboard joints are constructed by a combination of a joint compound and a matrix material to create a composite structure lending strength to the joint. Similar processes are also used to make wallboard repairs and/or finish inside and outside wall corners. One matrix material commonly used for wallboard joints is a rolled material, commonly referred to as “tape.” When constructing a joint, a layer of joint compound may be laid along a joint before a layer of tape is added along and covering the joint. One or more layer of joint compound may be added over the tape, and over each other, as is known. The resulting layers of dried joint compound and tape make up a composite joint structure that should be able to withstand various stresses such as tensile, compressive and shear stresses that may be present at the joint, such that cracks and breaks are avoided as wall structures may shift, settle or otherwise become stressed. However, this is not the case. Although composite joint structures are generally effective in withstanding tensile stresses, i.e., stresses tending to pull the joint apart, they are not sufficiently resilient against compressive or shear stresses tending to compress or slide the joint.
There are two conventional types of tape used in the art today. The first type, made of paper, includes a continuous or perforated tape strip that offers little to no strength in the compressive direction. The second type, made of fiberglass, is also weak in a compressive stress direction. In general, fiberglass tape is not ideal for stabilizing joints between drywall boards because, while it has cross-directional fibers (short fibers whose length is the width of the tape) that are strong in tension and provide excellent resistance to tensile forces pulling the joint apart, it provides almost no resistance to compressive forces that push the boards closer together. Numerous drywall joint strength tests have shown that fiberglass mesh tape makes a joint relatively strong when tensile forces are placed on the joint, but when compressive or shearing forces are placed on the joint, it fails easily. Joint failure manifests itself as joint compound cracking, which requires repair. For this reason, fiberglass joint tape is not recommended for use with drying type joint compounds, which are not as strong and crack-resistant as setting-type compounds.
Samples of a drywall joint made with Fibatape® tape have been tensile tested in accordance with ASTM C 474 (Appendix) which measures the strength to first crack of a tape-compound sample coated in electrically conductive paint. The strength is measured until the first crack in the paint occurs, which breaks the electrical continuity along the surface and registers the ultimate tensile load. Such failures suggest that typical taped joints do not optimize the strength of the glass-joint compound composite. In one mode of failure, tensile loads tend to separate the glass fibers from the joint compound matrix instead of transferring these loads to the glass fibers themselves.